Sponge-rubber articles, method of producing the same, and composition therefor



June 1 1926.

1,587,486 UCING THE SAME T. P. D. MARSHALL SPONGE RUBBER ARTICLES,METHOD OF PROD AND COMPOSITION THEREFOR Filed May 28, 1925 Patented June1, 1926.

UNITED; STATES PATENT OFFICE.

muons mm nouenns MARSHALL, or wmenam, ONTARIO cannon, "Assmnon OFONE-HALF To JOSHUA HIRST, OF WINGHAM, CANADA.

srOKGE-RUBBEB ARTICLES, METHOD OFII'RODUCING THE SAME, nnn'coiurosxrlon'rnEnEEoR. a

Application filed May 28,

The invention relates to improvements in the method of producing spongerubber tubes as described in the present specification. M

One objectof the invention is to produce a compositionofInatter'possessing the resilient characteristics of pneumatic deviceswithout the various objectionable .features thereof, thus rendering itmore .desirable for many purposes, such as the manufacture of innertubes for vehicle tires, kneeling pads, seat cushions and other articlesof a similar nature.

Pneumatic tubes for vehicle tires have always been most unsatisfactoryowing .to

the ease with which they can be punctured I and it is only for'the wantof a non-puncturable substitute having like resilient qualities thatthey have come'into such great use and it-is an object of the presentinvention to entirely replace these pneumatic tubes.

Another'ob ect is to produce an inner tubefor-vehicle tires which willnot only retain its original shape throughout its life but will alsoserve to preserve the contpur of the casin A further object is toprovide an inner tube which will not crack and which will have 'a smoothexterior.

A still further object is to provide? position of matter which is evenin Q1 and of great tensile strength.

And generally the objects of the invention are to provide a new,material combining the requirements. of resiliency, great tensilestrength, lightness and durability and which may be manufactured at alow cost.

The invention consists in the. improved composition of matter and in thenovel method of producing same, as described and claimed hereinafter.

The drawing is a cross sectional view through an inner tube for avehicle tire.

The ingredients which are employed in the production of'this newcomposition of matter are as follows: crude rubber, stearic acid,sulphur, litharge, oxide of zinc, and

compores] petroleum product, and'the proportions of each to the wholemay be varied according to the-various requirements of different ar-'ticles being manufactured, but it has been found that best results havebeen obtained in the manufacture of inner tubes for ve-' have beenobtained when the working 1925. Serial No. 33,578.

hicle tiresby usin these ingredients substantially in the fol owingproportions: rubber, 70-parts; 'stearic acid, 2 parts; sul.

phur, 10 parts; litharge,'21/ parts; oxide of zinc, 10 parts; andpetroleum .product, 5 parts.

In carrying out this process in the manufacture of inner tubes therubber is first worked on rollin nills until it attains a plasticcondition a-ft? Whicl1 the other ingredients are added in substantiallythe proportions set out above andthe whole is then thoroughly mixedtogether between rollers having a suitable speed variation (preferablyof about' 2% to- 1 revolutions). This resultant material is then rolledinto sheets which are then placed in stoves, or other suitable heatingapparatus, and subjected to heat at a suflicient temperature to bringthe material to a porous state. Best results have been obtained byproviding a heating temperature. of about- 100 degrees F. at whichtemperature it usually requires about 3 hours to bring the material to aproper porouscondition, but the degree of'heat ma be varied somewhatwith good results, in w ich case itwill probably be necessary to alsovary the length of time during which the material is subjected to theheat. The porous composition. thus obtained is then put on rolls andworked at a lower temperature than that to which it was subjectedtobring it to its porous state, the degree of heat being graduallyincreased during the working until it attains a temperature onlyslightly less than that required to bring it to its porous state. Thiscomparative chilling on the rolls during working tends to increase.

the tensile strength and producesa composition'which is even in thepores. Best-results is commenced in a temperature of about 30 to 40degrees F. and thistemperature is gradually increased to about 70 todegrees F. The material is then tubed by any desired process to therequired diameter and placed in moulds and allowedto stand until thegases form pores in the material which causes it toexpand tothe-required shape. It is then vulcanized in the ordinary way bysubjecting it to steam heat.

he inner tubes produced by the above method will be found tohave ahoneycomblike interior surrounded by a, comparatively terior.

VVhatI claim is 1. A method of producing sponge rubber tubes consistingin Working a quantity of crude rubber to a plastic state and mixingthoroughly therewith stearic acid, sulphur, litharge, oxide of zinc anda petroleum product, rolling the resultant plastic material into sheetsand subjecting same to heat until it attains a porous condition, thenworking on rollsat a temperature lower than that required to bringit tosaid porous condition, gradually increasing said temperature duringworking, tubing said material to the required diameter, then placingsame in moulds until the pores caused by the gases have expanded thematerial to the desired shape, and then vulcanizing.

2. As an article of manufacture, an inner tube comprising asubstantially honeycomblike interior having a comparatively denseenclosing wall, said tube consisting of a mixture of crude rubber,stearic acid, sulphur, litharge, oxide of zinc, and a petroleum roduct.

3. process of, producing inner tubes consisting of working a quantity ofcrude rubber to a plastic state, mixing therewith sulphur, stearic acid,litharge, oxide of zinc and an oleaginous matter, then bringing same toa porous state by heating, working the resultant material under varyingtemperature, tubing said material, placing same in moulds to permitexpansion, and vulcanizing.

4. As a article of manufacture, an inner tube for a vehicle tire,consisting of approximately 70 parts of crude rubber, 2 parts of stearicacid, 10 parts of sul hur, 2%), parts of lithar e, 10 parts of oxi eofzinc and 5 parts 0 a petroleum product, all of said ingredients beingthoroughly-mixed to fOIIll a plastic mass, rolling said mass into sheetsand subjecting the same to heat until porous, working. same on rolls ina gradually increasing heat, tubing said material to the requireddiameter, then placing same in moulds to permit of expansion to the re-,

quired shape, and vulcamzing;

5. A resilient composition of matter composed of crude rubber, staricacid, sulphur, litharge, oxide of zinc, and a petroleum product, mixedin varying proportions according to the use for which it is required.

Signed at Toronto, Ont, this 11th day of May, 1925.

THOMAS PERCY DOUGLAS MARSHALL.

